The present invention relates to an angle gearing, comprising a first shaft with a first bevel gear non-rotatably fixed on said first shaft and at least a second shaft with a second bevel gear non-rotatably fixed on said second shaft, said second bevel gear engaging the first bevel gear, at least the first shaft being provided with an attachment portion comprising a cylindrical splined distal portion and a conical proximal portion, the first conical gear having a bore with a corresponding splined portion and a conical portion.
Angle gearings of this type are used, for example in the lower transmission in marine outboard drive units. In the lower transmission in such a drive unit it is desirable to minimise the size of the gears, the primary reasons therefor being to keep the splash losses to a minimum and to keep the dimensions of the underwater housing to a minimum, this being advantageous for the drag resistance of the drive unit through the water. Also, it is normally less expensive to manufacture a small gear than a large gear. The technical development in the design and manufacture of gears has make it possible in marine outboard drive units for example, to use gears which are very small relative to the torque/power to be transmitted, especially in drive units with double counter-rotating propellers in which the gear load is distributed to two sides of the driving gear.
When high torque is to be transmitted from a small gear to its shaft, high demands are placed on the joint between the gear and the shaft and a mere splines connection is in many cases not sufficient. In a known angle gearing in a marine outboard drive unit, a connection of the type described by way of introduction is used, i.e. with a conical portion and a splined portion. The conical portion functions as a conical joint and therefore requires axial pretensioning. The transmittable torque is directly related to this pretensioning, which, if lost, will result in the splines having to transmit the entire torque, which they can do only temporarily. Furthermore, the driving function of the cone is lost and this will mean that the position of the driving gear relative to the driven gear will be incorrect.
In known angle gearings of the type described by way of introduction in marine outboard drive units, the shaft with the driving gear is made with a threaded end portion onto which a nut is screwed. The above described pretensioning is achieved by tightening the nut. This method of achieving the axial pretensioning can, however, cause problems due to the limited space available for the threaded end portion of the shaft with the driving gear. A short threaded portion will have a very short elastic elongation, which means that even a small movement or shrinkage up onto the cone will eliminate the entire pretension. Furthermore, narrow tolerances are placed on the angle between the conical portion of the shaft and its threaded portion.